tonight on "nightline" -- the wife of the party, the democratic national convention kicks off as president obama's secret weapon, his wife michelle, takes the stage to tell the country why they should give her husband another four years. new kid on the block. a 37-year-old mayor, a rising latino leader. tonight, julian castro delivers a history-making speech, can he do what a young obama did eight years ago, when he made the speech that launched his career. we're behind the scenes. and party on. the gloves are off. it's crunch time for president obama's campaign with the polls in a dead heat, can the democrats convince americans that things will be better the

second time around? good evening. i'm terry moran in charlotte, north carolina. day one of the democratic national convention. and here just, just a little while ago, michelle obama brought down the house. they had the signs "we love michelle." this one is prepackprepackaged, question about it. but the emotion response spontaneous, as michelle obama told the nation why she believes her husband deserves another four years in the white house. when she speaks of their love and dreams. no question about, michelle obama is the president's

advocate. she's the president's not so secret weapon. >> serving as your first lady is an honor and privilege. >> reporter: when she stepped in the spotlight tonight, michelle obama is taking into prime time a role she's groomed and honed into in the four years in the white house. first, advocate. >> so in the end for barack, these issues aren't political, they're personal, because barack knows what it means when a family struggles. >> reporter: she was a star here, the delegates clearly adore her. a star on a mission. with her husband in the fight of his political life. their future on the line, mrs. obama took her vast national audience into the past. their past, that young couple starting out. >> we learned about dignity and decency. that how hard you work matters more than how much you make. those are the values that barack and i and so many of you are

trying to pass on to our own children. that's who we are. >> reporter: and she spoke as only she could, of how the presidency has shaped barack obama. >> after so many struggles and triumphs and moments that have tested my husband in ways i never could have imagined, i have seen first hand that being president doesn't change who you are. no, it reveals who you are. >> reporter: tonight, michelle obama was basking zblau ining n the approval of the crowd here at the convention, but in a wider popularity that's considerably higher than her husband's. her years as first lady, healthy eating advocate, fashion icon have made her a celebrity and more. she had an approval rating of 66% in the recent gallup poll. >> not only do they realize how great she is, but popular now.

>> reporter: we got up on the convention floor with jodie kantor who wrote the book "the obamas." how much does this mean to them? >> it means everything. really, this election is a judgment. mitt romney has got essentially the country saying we gave the obama guy a shot, and we don't want to continue that. >> reporter: and right now, there are ominous trends for president obama, especially among women, a new abc news/"washington post" poll revealed a startling erosion, the president has gone from a 57% to 39 percent favorable/unfavorable rating to a 56/46 slit today. >> she's real to women. better than anybody else.

>> reporter: that, of course, is what ann romney was trying to do for her husband at the republican convention. >> i love you, women! >> reporter: they are so different, and yet each so crucial in this campaign. one became a lawyer and had a career in health care. one worked at home, raising five sons. as her husband and their daughters cozy on the couch watch back home in the white house, she joked pointedly about their youthful financial struggle. >> yeah, we were so young, so in love and so in debt. >> reporter: and perhaps they appeal to different kinds of women voters. we heard from the left of the spectrum here. did you see ann romney speak at the republican convention? >> i did. >> what did you make of that? >> i couldn't believe how it was, a little offensive. for a party that spends so many time trying to strip away

women's rights. >> reporter: but michelle obama's goals was to transcend all the differences so in the end, she spoke to all those women and men in her universal role as mom. >> if we want to give all of our children a foundation for their dreams, opportunities worthy of their promise, if we want to give them that sense of limitless possibilities, their belief that here in america there is always something better out there, if you're willing to work for it, then we must work like never before. and we must once again come together and stand together for the man we can trust to keep moving this great country forward. my husband, our president, barack obama. thank you. god bless you. god bless america.

>> michelle obama, she did bring down the house here. while she was here, it was the first day of school back in washington. and that was topic number one at the white house, we're told. up next, it wasn't just michelle obama's big night, it was a big night for a political newcomer. a rising star, julian castro who made a speech for the history books. we've been behind the scenes with him. up next. [ diana ] power was very important to me. we test-drove the camry, took it on the freeway, and it was just like -- this was the car for me. [ ryan ] it has stuff that guys like, like the rims and the sleekness to the body. and, then, had the bluetooth and the navigation that diana really wanted. [ diana ] and it was a sport edition, so it felt really grounded to the ground. [ man ] grounded to the ground? yes, yes! grounded to the ground. [ male announcer ] see their story and more at the camry effect. camry. from toyota.

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this is the choice before us. and to me, to my generation, and for all the generations to come, our choice is clear. our choice is a man whose always chosen us. a man who already is our president, barack obama. >> that was julian castro, the

37-year-old mayor of san antonio, texas. he had this crowd roaring and laughing as he delivered the keynote address here. and it was a stemwinder. abc's john quinones spent the day with him. >> reporter: julian castro spent most of today rehearsing in his hotel room. >> right now, i feel pretty good, relaxed. i'm sure a few minutes before i walk on stage i'll be nervous. >> reporter: for the 37-year-old mayor of san antonio the first hispanic ever chosen to give the keynote, it's been an extraordinary journey. we both grew up in the same neighborhood, i've known him for years. as we walked along the san antonio river, it began to sink it in. the first hispanic ever to give the keynote at a democratic national convention. it's a big deal. >> sure, i'm looking forward to

doing it. >> reporter: nervous? >> of course, a little bit. it's a combination of being both very excited and a little bit nervous. >> reporter: so nervous, in fact, the days before his address, castro met with these catholic nuns. >> i wanted to ask you all to say a little prayer for me, because i think i'm going to need it. >> reporter: this week, san antonio sent their mayor off to charlotte with a big fiesta. everyone knows this could launch castro's own political trajectory. eight years ago, it happened to a virtually unknown senator barack obama. he sat down with ted koppel. >> what is it, mr. obama, that you think you might solve with the delegates here? is there a theme, an issue? >> you know, i would say the most important issue that the people are feeling right now is the sense of an america that is

separated. >> reporter: the state senator from illinois ended up delivering the speech that made his career. >> there is not a liberal america. and a conservative america. there is the united states of america. >> obama gave the speech, the keynote, 2004, four years later, he's president. does this lie ahead for julian castro? >> he lived in illinois. i live in texas. it's one of the reddest states in the whole nation. >> reporter: there are ghosts in this convention center for anyone delivering the keynote. ghosts of surgery,ful and unsuccessful keynotes gone by. >> my fellow democrats. >> reporter: in 1988, the keynote by bill clinton at the dnc was widely jeered and almost derailed his career. and yet, four years later, clinton was elected president. but there are plenty of speakers no one remembers. julian castro feels the

pressure. why did obama pick you? >> i think that he and i see eye to eye on a lot of issues. i also think it's another signifier of the significance of h himself pan hispanics. >> reporter: his mother immigrated to the country, his brother joaquin is now running for congress. he's expected to win. tonight, he introduced julian. >> ours is a nation like no other. a place where great journeys can be made in a single generation. no matter who you are or where you come from, the path is always forward. >> reporter: you grew up in a community, you wind up going to stanford, and a law degree from harvard, you and your brother. how is that possible? >> we are very blessed to have a family that wanted to make sure we got a good education. >> they studied. >> reporter: julian's mother

rosie. >> this or that wasn't as important as having each other and having a good time with the money we did have. >> reporter: she's been a community activist in san antonio for decades. a woman who began taking her twins into the voting booth when they were just toddlers. >> i did that purposely hoping they would be engaged citizens to practice a democracy and vote for the people who you want to represent you. >> reporter: tonight there was their mother. >> my mother fought hard for civil rights so instead of a mop, i could hold a microphone. while she may be proud of me tonight, i've got to tell you mom, i'm even more proud of you. >> reporter: is america ready for an hispanic president? >> i believe so.

i believe our country has made tremendous progress even since my mother's generation. and i believe that the united states is ready for people of all different strides and genders to be president. >> reporter: and tonight, perhaps to stress that point, he delivered part of his speech in spanish. >> it begins with you. it begins now. [ speaking in spanish ] may god bless you. may god bless the united states of america. >> reporter: for "nightline," i'm john quinones. we'll be right back. w to make t. so, why let erectile dysfunction get in your way? talk to your doctor about viagra. 20 million men already have. ask your doctor if your heart is healthy enough for sex. do not take viagra if you take nitrates for chest pain; it may cause an unsafe drop in blood pressure. side effects include headache, flushing, upset stomach, and abnormal vision.

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back in charlotte now, after day one of the democratic national convention. how did they do? how did they kick off what they need, which is a convention to spark the base and get those undecideds. george will is with us and donna brazile as well. george, what's the verdict on that? >> convention, first of all is a pep rally there was pep and mayer? castro had it. he gave a quite traditional, unlike mr. christie's republican keynote. a convincing keynote address. happyfully inflamed the candidate. people like the happy lawyer up there, he was smiling all the way, even when doing violence

for the good name. michelle obama's challenge was different. she had to tell us something we didn't know. any modern president is an open book who has been reading himself to us incessantly. this president wrote two books about himself as a young man. so what can she tell us? she combatted the image of barack obama as cool and detached too too much, so. the no drama obama probably greats on some people in a country that's really frightened and unhappy. tonight, she tried to say he's not cool and not detached. >> so cheerfulness in castro, a long way in politics. and passion. what do you think, donna? >> inspirational. i think tonight, one, democrats to came to hear from the first lady. they came to hear what is going on in this country. and tonight, she answered it, she said president obama is not only a great dad, a wonderful husband but he's a proven

leader, and let me tell what you he's been up to. so she filled in many of the blanks that democrats have been longing to hear what this president has been fighting for. we know the values of middle class, and he's fighting for jobs but we also heard from speakers like mayor castro, he clarified the choice that we're going forward with a president who is showing that he knows how to fix the economy, stabilize the economy, or are we going back, that's, of course, mitt romney. this is an exciting night for the democrats. >> the big question is what's it going to be like in the four years? bill clinton said when times are rough, they want not inspiration, but explanation. >> that's barack obama's challenge, thursday night, he has to tell us what the second term going to be. is it going to be different? this is difficult because the american peel want something different because they're not

elated by the condition of the country after four years of his presidency. so he has to satisfy the desire for a second chapter, without in any way repudiating the first chapter. >> kind of a delicate line. donna, do you think there was a class discussion happening here? that what michelle obama and julian castro are saying that barack obama and the democrats are more like you than the republicans? >> look, there's no question, republicans are saying let's go back to trickle-down politics. michelle said let's grow the economy from the middle. middle class families, working class families, that's how we get america back on the road to prosperity. >> that's the new deal kind of strategy. they wanted to get democrats to jump to their feet, you talk about lifestyle, contraception, abortion, that's the three subjects tha